Enclosures are used for protecting, electrical junctions, switches, equipments, instruments, etc. from outdoor weathering conditions, thereby providing reliable service for the intended applications over an extended period of time requiring minimum maintenance.
Metal enclosures are still widely used mostly of steel, aluminium or SS. Metal enclosures need frequent painting in addition to finishing, surface treatment, galvanizing, etc. to provide extended weathering ability.
With wide acceptance of polymers, especially fibre reinforced polymer composites for outdoor use, several manufacturer's offer polymer enclosures.
These enclosures primarily comprise of two members, one a side wall assembly or enclosure body with provision for housing the equipment to be protected and a door or cover to seal the contents in the body.
The enclosure body is made with a integral continuous projection or tongue all around the upper periphery and the cover made with a matching integral continuous groove, fixed with a elastomeric seal preferably a seamless formed-in-place gasket. When the body and cover are held together by means of screws and nuts provided on the cover and body respectively or by means of hinges and fasteners, the elastomeric gasket gets compressed between the tongue and the groove and the enclosure gets sealed to achieve a high level of ingress protection.
Medium to large enclosures with increasing size with respect to length, breadth and depth, such or similar integral body and cover designs become expensive, due to high cost of moulds, process equipment, processing and transportation cost.
Some manufacturers attempted to make such medium to large enclosures in modular design, wherein the body is assembled with standard modules having a bottom, top and at least two sides and fitted with an integral rear cover and hinged or removable integral front cover. In some cases, a common rear and front covers are used.
The disadvantage in the above mentioned type of enclosure is that though the tongue formed integrally out of sides, top and bottom part of the body, is not continuous at the junctions resulting in reduced the level of ingress protection. In addition, as the cover is integral with a continuous groove, and the body parts are mostly made individually for each size, the mould costs and associated processing costs are still high.